What Is Run-Length Encoding; Immediate Commands; Compression Encoding Commands - Intermec EasyCoder 3240 Developer's Manual

Chapter 4 — Advanced Printer Programming

What Is Run-Length Encoding?

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When printing a label with direct graphics, you must have enough dynamic
RAM installed in your printer to contain the entire label. Because Intermec
printers normally reuse image bands, you can print long labels with
standard RAM; however, when you download direct graphics, the printer
retains no information regarding the existence of the graphic in its image
bands. Therefore, the printer cannot reuse those image bands when you
download a direct graphic.
With standard memory, you should be able to print almost any label up to
15.2 cm (6 in) long. You may need to install more memory for longer
labels.
Run-length encoding (RLE) is a method of compressing bitmap graphics.
RLE compresses graphics that have repeated runs of white or black dots in a
column, reducing the amount of time required to download the graphics to
a printer.
RLE sends a series of commands that define each bitmap column of a
graphic and takes advantage of a series of repeated dots within a column by
encoding them as transition commands. Instead of sending the entire
column of bitmap data, it sends commands telling the printer how many
series of black and white dots to image.
If columns are identical, a command can instruct the printer to repeat the
last column. RLE is ideal for bar code graphics or designs with simple
patterns.
In cases where patterns do not exist, you can send uncompressed bitmap
data to the printer. You can mix raw bitmap data and RLE commands to
ensure the most efficient way to download a graphic.
The RLE file may contain five types of data, each of which is one byte long:

Immediate Commands

Recognized and executed as regular IPL commands or protocol commands.
Syntax is removed from compressed data.
• Byte format (7-0): 000xxxx
• Range is 0 to 31

Compression Encoding Commands

Used as part of the compressed graphics file to change or set data modes,
repeat lines, change the origin for the next lines of data, or end the
compressed graphics file and return to IPL command printing.
• Byte format (7-0): 001xxxx
• Range is 32 to 63
Intermec Printer Language (IPL) Developer's Guide